A colloquial way to refer to ginger ale.
Referred to as such due to the fact that it's a readily available
drink option to have while riding a plane, whereas other soft drinks are offered more often under other circumstances, such as at restaurants and supermarkets.
When one wants a soft
drink, the first drinks that come to mind are, more often than not, everything else but ginger ale. However, since it'
s offered at plane rides, ginger ale sometimes associated with them, hence "plane
juice".